This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention.
No admission is necessarily intended, nor should be construed, that any of the preceding information, or the reference in the drawings to “prior art” constitutes prior art against the present invention.
When a well has been drilled in an underground hydrocarbon formation, the well is typically lined with cylindrical hollow casing (typically steel) to prevent collapse of the drilled well. Thus in order to “complete” a well in preparation for production of hydrocarbons from such cased well, the casing liner of the wellbore must first be perforated to allow hydrocarbons to be able to flow into the well.
Perforation of the wellbore casing must also precede the further “completion” step which is now typically carried out during most modern well completions, namely the further step of injecting a fracking fluid into the hydrocarbon formation via perforations in the wellbore casing, to thereby fracture the formation in the region of the well so as to create better recovery conditions and assist in flowing hydrocarbons out of the formation and into the wellbore.
Wellbore perforation has to date been conducted in three principle manners.
Firstly, wellbore perforations can be carried out by way of mechanical punch tools, which when inserted into a cased well and positioned at desired locations along a wellbore, punch a series of apertures in the steel casing at such locations where actuated to thereby perforate the casing.
Alternatively, casing perforation can be accomplished by way of detonation of explosive shaped charges at specific desired locations along a wellbore. In such method shaped explosive charges are inserted down a wellbore and electrically actuated to as to perforate the steel wellbore in the region of the placement of the shaped charges.
Alternatively, wellbore perforation can be accomplished by the use of a jetting tool which is inserted in the wellbore. An abrasive jetting fluid is supplied under high pressure to the jetting tool when positioned at a desired location along the wellbore. The jetting tool directs the jetting fluid outwardly in a pressure jet which impinges against the steel casing. Due to the continued abrasion of the directed high pressure jet against the side of the casing, the casing is perforated in the region of the jet(s).
U.S. Pat. No. 3,175,613 entitled “Well perforating with abrasive fluids”, teaches one method of perforating a wellbore using an abrasive jet which contains sand, an liquid, and a gas such as carbon dioxide or nitrogen, which is used as the jetting fluid.
Jetting tools and techniques for perforating wellbores using pressurized abrasive fluids have generally been improved upon over the years.
For example, Canadian Patent Application 2,873,541 entitled “Fracturing Valve and Fracturing String” teaches a downhole tool 200 used for both perforating a wellbore and further fracking the formation via the perforations created in the wellbore. A sliding mandrel 15, a frac port 60 which may be opened and closed by mandrel 15 acting as a valve, a compressive packer 121 located on the tool downhole of frac port 60, a “j’ slot 123, and a plurality of jetting nozzles 12 located at an upper end of tool 200, all incorporated into tool 200. FIGS. 7a, 8 & 9 show successive sequences in the positioning and operation of the tool 200 during “run-in” (FIG. 7a), “perforating” (FIG. 8), and “fracking” (FIG. 9). Specifically, the frac port 60 comprises a window on a tubular 1, and an outer sleeve is disposed around the tubular which is slidable relative to the tubular, the outer sleeve having a port, wherein for (frac) fluid to exit the valve the window and port must each be aligned by relative movement to each other. Disadvantageously, however, the jetting nozzles 12 on such tool 200 have no means of being closed to prevent ingress of detritus and cuttings during “run-in” of tool 200 into the wellbore.
Canadian patent application CA 2,738,907 entitled “Tools and Methods of Use in Completion of a Wellbore” teaches a sand jetting tool 100 having an abrasive jet assembly 10, a ‘j’ slot, and a single compressible seal 11 (FIG. 1a). The method disclosed therein is directed to an embodiment having a moveable slidable sleeve 41 secured by a shear pin, and using a locator to grip the sleeve 41 with slips to move sleeve 41 to open jetting ports 42, as shown in FIG. 4a, 4b thereof. Disadvantageously, therefore, the jetting ports 42 must be opened by inserting a special locator tool into the wellbore.
Canadian patent CA 2,693,676 teaches a sand jet tool 30 having a ball-actuated sandjet port, and an expandable packer 31 that is actuated by a “j” slot. The tool 30 has a debris relief passageway that is operatively associated with the ‘j’ slot and actuated (opened and closed) by movement of the ‘J’ slot.
Canadian patent 2,713,611 teaches a perforating and fracking tool having a sandjet perforating assembly 80, a “j”-slot for actuating resettable anchor device 41, and a bypass plug operating as a valve which allows equalization of pressure in a straddle zone 10 between cup seals 20, 30, to release pressure, when desired, between cup seals 20, 30, as shown in FIG. 1.
U.S. Pat. No. 6,394,184 teaches a system and method for perforating and fracking a formation having a wellbore therein. Although perforating guns 136,146,156 are shown in some of the drawings, the disclosure teaches that the “perforating means” may also comprise an abrasive fluid-jet cutting device (ref. page 11, lines 13-15 and page 37, lines 5-6) and further in FIG. 10 thereof depicts such a device 310.
US publication 2014/0158361 relates to a multi-shift frac sleeve system 10 which uses a pressure actuated spring-biased sleeve 22 for opening and closing a frac port 18, which may be further actuated to move to a third position (FIG. 4) where frac port 18 is closed, as may be seen from FIGS. 2-5 thereof. It teaches a pin 20 and ‘j’ slot 27 for controlling shifting of inner sleeve 14. Again, to open the frac ports 18, such patent application teaches an outer sleeve and an inner sleeve where the ports therein must be aligned in order for passage of fluid therethrough.
Canadian patent 2,611,928 teaches layers of staggered jet nozzles, wherein the jetting fluid is further used to frac the formation.
Canadian patent application CA 2,843,619 titled “Downhole Tool Assembly with Debris Relief and Method for using Same” as per CA 2,693,676 (above) makes similar disclosure as CA 2,693,676, but requires that the debris relief valve be actuated by movement of the tool up or down, and not by a pressure differential.
CA 2,856,184, similar to CA 2,873,541, relates to a downhole tool capable of performing both abrasive jet perforation as well as fracturing, with a valve portion made up of a tubular mandrel having a through bore continuous with a tubing string, and a frac window through the side of the tubular mandrel. Jet nozzle 98 is used for perforating (with the frac port closed and seal 121 deactivated) as shown in FIG. 11A thereof. FIG. 11B shows the tool moved upwardly so that the frac window is open and positioned next to the created perforations 98 for fracking (seal 121 is activated). Again, the tubular and sleeve are each axially moveable relative to one another, and the valve is move to the closed position by applying a mechanical force to the tubular (i.e. raising it upwardly), as shown in FIG. 8, as opposed to the application of fluid pressure to the upper region of the tool
CA 2,224,571/U.S. Pat. No. 5,765,642 teaches a jetting tool having an expandable packer, having at least one fluid jet forming nozzle, wherein the jetting fluid is used to further frac the formation.